The urinary tract, especially the bladder, is one of the most common sites of bacterial infection in humans. Uropathogenic Escherichia coli (UPEC) is the predominant cause of urinary tract infection (UTI). Women, children, the elderly, and individuals with catheters, uroliths, or diabetes mellitus are highly susceptible to UTI. There is an immediate need for novel strategies to manage UTI because of an alarming increase in antibiotic resistance in UPEC globally. We have demonstrated that copper (Cu) is mobilized to urine as a host response during clinical UTI in patients. We have developed a non-human primate model of UTI that recapitulates urinary Cu mobilization observed in human UTI. Our findings, taken together with reports of fulminant UTI in patients with Menkes disease (who cannot absorb dietary Cu), highlight an important and novel biological role for Cu in the protection against UTI. Our long-term research goal is to define the molecular and cellular features of host-pathogen interaction during UTI to identify targets for therapeutic development. Major objectives of this proposal are to define the mechanism of Cu-mediated protection against UPEC colonization, and to determine how Cu is mobilized to urine during UTI. Based on our published and preliminary data, we hypothesize that Cu is mobilized to urine in response to UPEC signals to impede bacterial survival, and that augmenting the toxicity of Cu will promote UPEC clearance. The rationale for the proposed work is that understanding Cu mobilization, and its impact on UPEC survival are critical to develop therapeutics that bolster this innate response to resolve UTI. We will test our central hypothesis by pursuing the following specific aims: 1) Determine how copper deters UPEC survival, and identify pathogen signals that trigger copper mobilization; 2) Define the mechanism of copper-mediated UPEC killing within human phagocytes; and 3) Determine the effect of augmenting the toxicity of copper on UPEC clearance. The expected outcomes of this study include understanding the direct and indirect impact of Cu on UPEC clearance during UTI, and the identification of the pathogen signals that trigger Cu mobilization. We will determine the mechanism of Cu-mediated UPEC killing in human phagocytes. Cu-boosting treatments are anticipated to promote UPEC clearance in the mouse and non-human primate models of UTI. The substantial positive impact of this study will be elucidating the role of an innate host defense effector in protection against UTI in humans. The proposed research is significant because our findings are anticipated to break new ground to develop novel interventions against UTI. Our approach is innovative because we seek to bolster a host effector that is amenable to dietary and pharmacological modulation, to promote resolution of UTI. In summary, the proposed study is expected to confer a significant public health benefit against UTI, a ubiquitous and profoundly painful infectious disease affecting millions of people.